Journal of Thermal Analysis and Calorimetry
Volume/Issue:
Volume 57: Issue 1
Thermal Analysis, Microcalorimetry and Combined Techniques for the Study of the Polymorphic Behaviour of a Purine Derivative
Authors:
D. Giron
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,
P. Piechon
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C. Goldbronn
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, and
S. Pfeffer
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Pages:
61–73
Online Publication Date:
03 Nov 2004
Publication Date:
25 Jul 1999
Article Category:
Research Article
DOI:
https://doi.org/10.1023/a:1010145125531
Keywords:
amorphous; combined techniques for polymorphism; DSC; MKS 492; polymorphism; purine; quantitative determination ofamorphous and polymorphs; solvent mediated transitions; temperature resolved X-ray diffraction; TG; thermodynamic relation between polymorphs; xanthine
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Abstract  

The polymorphic behaviour of the purine derivative MKS 492 was studied with investigations of suspensions of selected samples in different solvents and of samples obtained by crystallizations. The samples were analyzed by DSC, TG and X-ray diffraction. Six different crystalline modifications called A, B, B, C, D and E and an amorphous form were identified. Four pure crystalline modifications, A, B, C and D have been manufactured and characterized by DSC, X-ray, IR, solubilities, densities, hygroscopicity and dissolution measurements. The four forms A, C, D and E are monotrop to the form B. The form B is enantiotrop to the form B, which revealed the highest melting point of all known polymorphs. This form B is only stable at high temperature. Temperature resolved X-ray diffraction was very helpful for proper interpretation of the thermal events. The melting peaks of the forms A and C and the endothermic peak corresponding to the enantiotropic transition B into B occur in a narrow range of temperature. The form B which is the most stable one at room temperature has been chosen for further development. Quantitative methods to determine the content of the forms A, C and D in samples of form B or to determine the content of form A, B and D in form C have been developed by using X-ray diffraction. Limits of detection are 1 or 2%. For the quantitative determination of the amorphous fraction, X-ray diffraction and microcalorimetry are compared. For high amounts of the amorphous fraction, the X-ray diffraction method is preferred because it is faster. Microcalorimetry is very attractive for levels below 10% amorphous content. The lowest limit of detection is obtained by microcalorimetry, about 1%.

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Cover Journal of Thermal Analysis and Calorimetry
Journal of Thermal Analysis and Calorimetry
Print ISSN:
1388-6150
Online ISSN:
1572-8943

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation		 1969
Volumes
per Year		 1
Issues
per Year		 24
Founder Akadémiai Kiadó
Founder's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher		 Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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